1. FIELD OF THE INVENTION
This invention relates to a spreader bar apparatus for separating slit portions of a web. More particularly, this invention relates to a spreader bar apparatus which includes porous layers for reducing the noise level generated by movement of the web over the spreader bars.
2. Information Disclosure Statement
In the papermaking industry, a web of paper is formed from stock in a forming section. The formed web is then pressed for removing a substantial portion of the water from the web. Thereafter, the pressed web extends through a drying section for removing a further portion of water from the pressed web. Next, the dried web is guided through a calender for smoothing the surface of the dried web. Finally, the web is guided from the calender to a reeling apparatus where the web is wound onto a reel which has a length of 30 or more feet and a diameter of 5 or more feet.
Typically, the wound reel of paper is rewound in order to provide wound rolls having a length of between 1 to 5 feet.
In order to cut the large reel into more manageable rolls of paper, the web is rewound from the reel over a stationary spreader bar. Rotating slitting knives are disposed in spaced axial relationship along the cross-machine direction relative to the web between the reel being unwound and the spreader bar.
As the slit portions extend over and around a bowed spreader bar, the slit portions of the web separate axially relative to each other. Such separated slit portions are then guided around a further spreader bar which is bowed such that the separated slit portions are disposed parallel relative to each other.
The separated parallel slit portions are then rewound onto individual reels having a length corresponding to the spacing between adjacent slitters.
In view of the high speeds at which the web is guided around the spreader bars, a problem has existed in that considerable frictional resistance is generated between the spreader bars and the web as the web extends around the spreader bars.
Additionally and more importantly, the noise level caused by the movement of the slit portions moving relative to the spreader bars is extremely high and such noise level has sometimes caused health problems amongst operating personnel.
One attempt to reduce the noise level of spreader bars is disclosed in U.S. Pat. No. 4,300,714 to Dahl et al, issued Nov. 17, 1981. U.S. Pat. No. 4,300,714 discloses baffle bars attached to the curved bars in order to eliminate the Coanda effect of air tending to follow the curvature of the stationary cylinders of the spreader bars. However in the aforementioned arrangement, once the baffle bars were attached to the spreader bars, the ability to rotate the spreader bars in order to accommodate different grades of paper was virtually eliminated.
The present invention overcomes the aforementioned problem by the provision of porous layers secured to the spreader bars to replace the air supply holes used in the prior art arrangements. The air is supplied through the porous media to provide a uniform cushion of air to efficiently float the paper web over the curvature of the bars without being influenced by the Coanda effect.
Therefore, it is a primary object of the present invention to provide a spreader bar apparatus that overcomes the aforementioned inadequacies of the prior art arrangements and that provides a considerable contribution to the art of rewinding paper webs.